One technique to increase dynamic range of a CMOS active pixel imager is to amplify pixel signals using two separate signal gains. The first applied gain is usually smaller than the second. The two amplified pixel signals are later combined together to produce the actual pixel output signal.
Since the currently adopted column parallel architecture uses a destructive read-out scheme, multiple exposures of the CMOS imager pixel array are required to capture pixel signals for each of the applied gain values. Sampling multiple exposures is a time consuming process, limiting the speed of image capture.